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in rhel 5 when i am executing following comman it run:
mount -t cifs //158.13.0.1/d$ /mnt -o user=username
but when i run following command it does not run
mount -t cifs //158.13.0.1/d$ /mnt -o rw user=username

each -whatever, in any unix command must be followed by an
argument *whitout* spaces
as each space is interpreted as a separator,
try using another -o, that is -o rw -o user= or a comma,
-o rw,user=you